(1) Field of the Invention
The present invention relates to an image display control apparatus or the like that controls light transmittance of liquid crystals of a liquid crystal display (LCD) screen for displaying images based on an inputted image signal and controls, according to the light transmittance of the liquid crystals, an amount of light emitted by a backlight for illuminating the back of the LCD screen based on the image signal.
(2) Description of the Related Art
In recent years, apparatuses for controlling LCD screens have been widely used as image display apparatuses for mobile information terminals such as notebook computers. This type of an image display apparatus controls light transmittance of liquid crystals of an LCD screen on a pixel-by-pixel basis based on image data and displays images on the LCD screen by illuminating the back of the LCD screen using a backlight.
LCD screens are thin and compact, and thus heavily used for mobile information terminals such as notebook computers. However, to take a notebook computer as an example, power consumption of a backlight is about 5W, which accounts for about a quarter to a half of the entire power consumption of the computer. Since such a mobile information terminal is structured so as to operate by batteries or the like, how to reduce power consumption is a big problem.
A conventional image display apparatus will be explained with reference to the drawings.
FIG. 1 is a block diagram showing a structure of a conventional image display apparatus.
The image display apparatus includes an LCD screen 920 and an image display control apparatus 900 for controlling an amount of light emitted by a backlight 921. In the image display control apparatus 900, a data analysis unit 901 obtains, based on image data inputted from an image memory 910, an acceptable limit within which brightness of an image can be increased, a data control unit 902 controls the brightness of the image data based on the obtained limit, and an image controller 903 generates a driving signal based on the controlled image data to have the LCD screen 920 display the image. A dimmer 904 controls an amount of light emitted by the backlight 921 according to the limit obtained by the data analysis unit 901.
As a result, in order to reduce the power consumption, the image display control apparatus 900 controls the image data so as to increase the light transmittance of the LCD screen 920 as much as possible and instead lower the amount of light emitted by the backlight 921 accordingly to the increase of the light transmittance, and thus displays the image of the same quality as that displayed without controlling the image data nor the light amount emitted by the backlight (See Japanese Laid-Open Patent Application No. H11-65531).
However, in the image display control apparatus 900 of the above-mentioned conventional image display apparatus, the data analysis unit 901, the data control unit 902 and others use a lot of resources such as multiplication units, so the circuit in the image display control apparatus becomes large in size. As a result, the conventional image display apparatus has a problem that a mobile information terminal such as a notebook computer becomes large in size when such an image display control apparatus is integrated into the mobile information terminal.